Suberites montiniger : Carter 1880

Suberites montiniger Carter, 1880

(Fig. 7a–e 1)

Suberites montiniger: Carter 1880, p. 256 –257; Vosmaer 1882, p. 31 –32; pl. I, fig. 26; pl. IV, figs 137–139; Topsent 1892, p. 130.

Suberites crelloides: Marenzeller 1886.

Pseudosuberites montiniger: Hentschel 1916, pp. 6–7; Hentschel 1929, p. 870;

Stylotella gorbunovi: Rezvoi 1931, p. 510 –512, figs 3–5.

Not S. montiniger: Lambe 1894, p. 128; Topsent 1915, pp. 39–40; Koltun 1964b, p. 24.

+ Suberites glasenappii: Merejkowsky 1877, pp. 259–260. Swartschewsky 1906, pp. 319–320, pl. 13, fig. 5.

Material analyzed. Kara Sea, PINRO trawl survey, Pomor, 1994, st. 50 (69.9866N, 60.3183E), depth 58 m (1 specimen; KFU-LH-2/018).

Barents Sea, PINRO trawl survey, Muklevich, 2003, st. 94 (70.9981N, 42.9705E), depth 100 m, temperature 1.7 °C, salinity 34.606 psu (4 specimens; KFU-LH-2/019); st. 42 (70.4915N, 35.96E), depth 179 m, temperature 2.4 °C, salinity 34.911 psu (1 specimen); st. 30 (70.0118N, 33.4069E), depth 145 m, temperature 3.28 °C, salinity 34.526 psu (1 specimen). F. Nansen, 2004, st. 59 (73.5N, 52.59E), depth 76 m, temperature -0.37 °C, salinity 34.791 psu (8 specimens; KFU-LH-2/020).

East-Siberian Sea, MMBI trawl survey, Dalniye Zelentsy, 2014, st. A30 (76.655N, 147.9033E), depth 36 m (1 specimen; KFU-LH-2/021).

Description. Sponge hemispherical or disc-shaped, up to 3 cm in diameter by 1.5 cm thick. It often grows attached on barnacles or small pebbles. A single apical, roundish or slit-like osculum is surrounded by a short spicular collar (Fig. 7a). Sometimes there are a few smaller oscula on the sides. The outer surface seems to be absolutely smooth and even to touch, yet it is covered with slightly projecting circular elevations (up to ~ 1 mm length) or reduced papillae, leading to subdermal cavities and giving the surface a characteristic pattern (Fig. 7b). The dermal membrane is a thin and transparent film devoid of spicules. Sponge firm and elastic. Colour from gray to russet.

Spicules of one kind only: slightly sinuous subtylostyles with a barely visible basal swelling, 238–281±23–335 × 2.3–3.7±0.6–4.8 (n = 85) µm (Fig. 7e–e 2).

Skeleton is typical for genus, with ill-defined choanosomal reticulation of spicula-tracts and single spicules. Only near the surface spicules become arranged into radial bundles, ending in bouquets in the ectosome.

Remarks. Originally assigned to the genus Suberites by Carter (1880), this sponge was subsequently relocated to Pseudosuberites Topsent 1896 by Hentschel (1916; 1929), since he found a tangential layer of spicules in the dermal membrane in specimens from Svalbard —a distinctive difference of Pseudosuberites as compared to Suberites. However, none of the specimens analyzed in this work, including a number of specimens from the Barents Sea, Kara and Laptev Seas, shared this skeletal feature: no tangentially oriented spicules in the dermal membrane were found (Fig. 7c, d).

Marenzeller (1895) described a new sponge species from the Jan Mayen and commented that his rationale for considering Suberites crelloides a distinct species was based on the presence of surface papillae in his specimens—a feature hitherto never noted for S. montiniger. Subsequently both Hentschel (1916) and Rezvoi (1931) mentioned these were also common on the surface of Barents Sea specimens (Fig. 7c, d). Since spicule shape and dimensions are indistinguishable in the two sponges, we should consider S. crelloides merely a junior synonym of S. montiniger.

Suberites montiniger s. lat. has been recorded from all corners of the globe and apparently constitutes a species complex:

1) Lambe (1894, p. 128) doubted whether to refer his specimen from the north-east Pacific to S. montiniger since it had tylostyles (not subtylostyles) averaging 16 μm thickness, compared to 4–5 μm for the arctic specimens. Apparently he dealt with another species.

2) Both Topsent (1915, pp. 39–40) and Koltun (1964b) assigned Antarctic specimens to S. montiniger. Both authors mentioned the same kind of subtylostyles that were found in the Arctic specimens, yet the measurement ranges were different, with Antarctic specimens having spicules twice as large, averaging 450 by 10 µm Koltun (1964b). These slight morphological differences may indicate that the two groups of representatives for S. montiniger (Arctic vs. Antarctic) were separated relatively recently, probably with the retreat of the Last Glacial Maximum (Morozov et al., 2021).

3) Merejkowsky (1877) argued that “ White Sea sponge fauna stands apart with respect to other arctic seas as being highly endemic … and many species well known from the other seas, often show slight morphological deviations in spicules for the White Sea specimens ”. Suberites glasenappii, allocated by Merejkowsky (1877, pp. 259–260) remarkably resembled S. montiniger, yet subtylostyle illustrations and measurements (130–210 by 2–6 µm) for the White Sea specimens provided by Swartschewsky (1906, pp. 319–320), clearly indicate that we are dealing with a distinct species.